note: i am explaining this very carefully, because i do not know the skill or level or knowledge that you have. please do not take offense to my post, as i am trying to cover all the bases)
to properly time your engine to check and adjust the valves, you need to know a few things: valve lash, and to be 100% sure that the cylinder you are going to check/adjust is at top dead center compression, and not top dead center overlap. the term 4 stroke, which is what your motor is, means that the engine makes for strokes to complete the combustion cycle: the piston is at the top of its travel two times(TDC)top dead center compression and TDC overlap. the piston is at the bottom of its travel two times as well for compression BDC(bottom dead center) and exhaust BDC. top properly set the valve clearance or check the clearance the motor MUST be on TDC compression. you can physically adjust the valves on TDC overlap, but then your adjustment will be way off, and your valves will make noise from excessive clearance(tap tap tap noise)
so first, i recommend removing the fuel tank and other components to gain access to the top of the engine. when you do, you need to remove the flat rectangle covers on the top that cover the rocker arms. the valve adjustment method on this engine is "screw and locknut" whic his very easy. you dont need to remove teh cam, or even the cylinder head cover to check or adjust the valves. after the top rocker arm coves are removed(each cover has 2 bolts and an o-ring) you can see the rocker arms and screw and locknuts.
i recommend you remove these covers first before you set the engine at TDC compression so you can see the valves moving, and then you will know you are on the right TDC.
on the left side of your engine, on the flywheel cover. if you look at the pull start, directly next to it on the aluminum engine cover, on the top side you will see a plug that has a spot of an allen tool to remove it. you can see the picture i have provided, and you see that near the bottom of the picture is the flywheel side cover for the engine (#14) has the plug on top (#16).
you need to remove the plug(#14) and inside you will see the flywheel. now, you also need to remove the recoil(pull start) cover which comes off after removing the 4 small bolts around the edge.
at this time, you can now turn the engine with a socket and ratchet on that bolt that comes out where the recoil pull starter was. make sure you turn the engine the same direction as the pull starter does. you can look on the inside of it, and see which way the small gear in the middle will turn.(i cant recall which way the motor turns at this point)
now, with the recoil starter cover off, the plug for the timing mark on flywheel cover is removed, and you can see the rocker arms inside, we can properly set the engine to TDC compression and check the valves.
as you turn the engine, you will see the rocker arms moving up and down. first watch them as you turn the engine over. first, you will see the intake rocker arm move down, then up(INTAKE STROKE). this is where TDC compression is located at this interval. then you will see the exhaust valve move down, and then as it is almost done moving up the intake valve will start to push down.(this is TDC overlap) after you see the intake rocker arm move down then up, look through the flywheel inspection plug. turn VERY SLOW so you dont miss the mark. you will first see a small "F", then a line directly after it. right after that, you will see a "T" and a line. make sure you line up that line for the "T" with the small indicator line machined into the flywheel inspection hole.(you should see a small line in the middle of the inspection hole you are looking through)
now, with the "T" line lined up with the machined line, you are ready to check and adjust the valves!! the valve clearance for the intake valves are 0.002" to 0.004" . the spec for exhaust valves are 0.004" to 0.007". usually, a little on the looser side of the clearance is better to allow more time between valve adjustments.
be sure you check the valve lash when engine is cold, and the clearance feeler gauge is flat when inbetween the rocker arm and valve.
good luck! please let me know if i missed mosething, or you need more infor. or even if you need the clearance in mm instead of inches!!